Automatically update the last update date of a row in a Google Spreadsheet

google-app-script.js

function onEdit(edit) {
    var row = edit.range.getRow()
    var timestampTimeZone = "GMT+1"
    var timestampFormat = "dd/MM/yyyy"
    if( row >=2 ){
      var timestamp = Utilities.formatDate(
        new Date(),
        timestampTimeZone,
        timestampFormat)
      SpreadsheetApp
        .getActiveSpreadsheet()
        .getRange('Comunidades!D'+row) // Change to the cell you want to update
        .setValue(timestamp)
    } 
}